1. Field of the Invention
The present invention relates to a heat treatment method for a steel material.
2. Description of Related Art
In general, in order to produce a steel material having a predetermined hardness, the hardness of the steel material is increased by performing a quenching treatment on the steel material, and after that, the hardness of the steel material is adjusted by performing a tempering treatment on the steel material. Japanese Unexamined Patent Application Publication No. H06-108144 discloses a technique relating to a heat treatment method for a steel material which is capable of keeping the hardness of a steel material after tempering, while shortening a heat treatment time for tempering, and preventing formation of a martensitic structure during cooling.